// dear imgui: Platform Backend for GLFW
// This needs to be used along with a Renderer (e.g. OpenGL3, Vulkan, WebGPU..)
// (Info: GLFW is a cross-platform general purpose library for handling windows, inputs, OpenGL/Vulkan graphics context creation, etc.)
// (Requires: GLFW 3.1+)

// Implemented features:
//  [X] Platform: Clipboard support.
//  [X] Platform: Gamepad support. Enable with 'io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad'.
//  [X] Platform: Mouse cursor shape and visibility. Disable with 'io.ConfigFlags |= ImGuiConfigFlags_NoMouseCursorChange' (note: the resizing cursors requires GLFW 3.4+).
//  [X] Platform: Keyboard arrays indexed using GLFW_KEY_* codes, e.g. ImGui::IsKeyPressed(GLFW_KEY_SPACE).

// You can use unmodified imgui_impl_* files in your project. See examples/ folder for examples of using this.
// Prefer including the entire imgui/ repository into your project (either as a copy or as a submodule), and only build the backends you need.
// If you are new to Dear ImGui, read documentation from the docs/ folder + read the top of imgui.cpp.
// Read online: https://github.com/ocornut/imgui/tree/master/docs

// CHANGELOG
// (minor and older changes stripped away, please see git history for details)
//  2020-01-17: Inputs: Disable error callback while assigning mouse cursors because some X11 setup don't have them and it generates errors.
//  2019-12-05: Inputs: Added support for new mouse cursors added in GLFW 3.4+ (resizing cursors, not allowed cursor).
//  2019-10-18: Misc: Previously installed user callbacks are now restored on shutdown.
//  2019-07-21: Inputs: Added mapping for ImGuiKey_KeyPadEnter.
//  2019-05-11: Inputs: Don't filter value from character callback before calling AddInputCharacter().
//  2019-03-12: Misc: Preserve DisplayFramebufferScale when main window is minimized.
//  2018-11-30: Misc: Setting up io.BackendPlatformName so it can be displayed in the About Window.
//  2018-11-07: Inputs: When installing our GLFW callbacks, we save user's previously installed ones - if any - and chain call them.
//  2018-08-01: Inputs: Workaround for Emscripten which doesn't seem to handle focus related calls.
//  2018-06-29: Inputs: Added support for the ImGuiMouseCursor_Hand cursor.
//  2018-06-08: Misc: Extracted imgui_impl_glfw.cpp/.h away from the old combined GLFW+OpenGL/Vulkan examples.
//  2018-03-20: Misc: Setup io.BackendFlags ImGuiBackendFlags_HasMouseCursors flag + honor ImGuiConfigFlags_NoMouseCursorChange flag.
//  2018-02-20: Inputs: Added support for mouse cursors (ImGui::GetMouseCursor() value, passed to glfwSetCursor()).
//  2018-02-06: Misc: Removed call to ImGui::Shutdown() which is not available from 1.60 WIP, user needs to call CreateContext/DestroyContext themselves.
//  2018-02-06: Inputs: Added mapping for ImGuiKey_Space.
//  2018-01-25: Inputs: Added gamepad support if ImGuiConfigFlags_NavEnableGamepad is set.
//  2018-01-25: Inputs: Honoring the io.WantSetMousePos by repositioning the mouse (when using navigation and ImGuiConfigFlags_NavMoveMouse is set).
//  2018-01-20: Inputs: Added Horizontal Mouse Wheel support.
//  2018-01-18: Inputs: Added mapping for ImGuiKey_Insert.
//  2017-08-25: Inputs: MousePos set to -FLT_MAX,-FLT_MAX when mouse is unavailable/missing (instead of -1,-1).
//  2016-10-15: Misc: Added a void* user_data parameter to Clipboard function handlers.

#include <unordered_map>

#include <imgui/imgui.h>
#include <gui/imgui_impl_glfw.h>

// GLFW
#include <glad/glad.h>
#include <GLFW/glfw3.h>
#ifdef _WIN32
#undef APIENTRY
#define GLFW_EXPOSE_NATIVE_WIN32
#include <GLFW/glfw3native.h>// for glfwGetWin32Window
#endif
#define GLFW_HAS_WINDOW_TOPMOST (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3200) // 3.2+ GLFW_FLOATING
#define GLFW_HAS_WINDOW_HOVERED (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300) // 3.3+ GLFW_HOVERED
#define GLFW_HAS_WINDOW_ALPHA (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300)   // 3.3+ glfwSetWindowOpacity
#define GLFW_HAS_PER_MONITOR_DPI (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3300)// 3.3+ glfwGetMonitorContentScale
#define GLFW_HAS_VULKAN (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3200)         // 3.2+ glfwCreateWindowSurface
#ifdef GLFW_RESIZE_NESW_CURSOR                                                                 // let's be nice to people who pulled GLFW between 2019-04-16 (3.4 define) and 2019-11-29 (cursors defines) // FIXME: Remove when GLFW 3.4 is released?
#define GLFW_HAS_NEW_CURSORS (GLFW_VERSION_MAJOR * 1000 + GLFW_VERSION_MINOR * 100 >= 3400)    // 3.4+ GLFW_RESIZE_ALL_CURSOR, GLFW_RESIZE_NESW_CURSOR, GLFW_RESIZE_NWSE_CURSOR, GLFW_NOT_ALLOWED_CURSOR
#else
#define GLFW_HAS_NEW_CURSORS (0)
#endif

// Data
struct ImGuiGlfwContext {
    double m_Time = 0.0;
    bool m_MouseJustPressed[ImGuiMouseButton_COUNT] = {};
    GLFWcursor *m_MouseCursors[ImGuiMouseCursor_COUNT] = {};
};

[[nodiscard]] static auto &get_registry() noexcept {
    static std::unordered_map<GLFWwindow *, ImGuiGlfwContext> registry;
    return registry;
}

static const char *ImGui_ImplGlfw_GetClipboardText(void *user_data) {
    return glfwGetClipboardString((GLFWwindow *)user_data);
}

static void ImGui_ImplGlfw_SetClipboardText(void *user_data, const char *text) {
    glfwSetClipboardString((GLFWwindow *)user_data, text);
}

void ImGui_ImplGlfw_MouseButtonCallback(GLFWwindow *window, int button, int action, int mods) {
    auto &&ctx = get_registry()[window];
    if (action == GLFW_PRESS && button >= 0 && button < IM_ARRAYSIZE(ctx.m_MouseJustPressed)) {
        ctx.m_MouseJustPressed[button] = true;
    }
}

void ImGui_ImplGlfw_ScrollCallback(GLFWwindow *window, double xoffset, double yoffset) {
    ImGuiIO &io = ImGui::GetIO();
    io.MouseWheelH += (float)xoffset;
    io.MouseWheel += (float)yoffset;
}

void ImGui_ImplGlfw_KeyCallback(GLFWwindow *window, int key, int scancode, int action, int mods) {

    ImGuiIO &io = ImGui::GetIO();
    if (key >= 0 && key < IM_ARRAYSIZE(io.KeysDown)) {
        if (action == GLFW_PRESS)
            io.KeysDown[key] = true;
        if (action == GLFW_RELEASE)
            io.KeysDown[key] = false;
    }

    // Modifiers are not reliable across systems
    io.KeyCtrl = io.KeysDown[GLFW_KEY_LEFT_CONTROL] || io.KeysDown[GLFW_KEY_RIGHT_CONTROL];
    io.KeyShift = io.KeysDown[GLFW_KEY_LEFT_SHIFT] || io.KeysDown[GLFW_KEY_RIGHT_SHIFT];
    io.KeyAlt = io.KeysDown[GLFW_KEY_LEFT_ALT] || io.KeysDown[GLFW_KEY_RIGHT_ALT];
#ifdef _WIN32
    io.KeySuper = false;
#else
    io.KeySuper = io.KeysDown[GLFW_KEY_LEFT_SUPER] || io.KeysDown[GLFW_KEY_RIGHT_SUPER];
#endif
}

void ImGui_ImplGlfw_CharCallback(GLFWwindow *window, unsigned int c) {
    ImGuiIO &io = ImGui::GetIO();
    io.AddInputCharacter(c);
}

static bool ImGui_ImplGlfw_Init(GLFWwindow *window) {
    // Setup backend capabilities flags
    ImGuiIO &io = ImGui::GetIO();
    io.BackendFlags |= ImGuiBackendFlags_HasMouseCursors;// We can honor GetMouseCursor() values (optional)
    io.BackendFlags |= ImGuiBackendFlags_HasSetMousePos; // We can honor io.WantSetMousePos requests (optional, rarely used)
    io.BackendPlatformName = "imgui_impl_glfw";

    // Keyboard mapping. Dear ImGui will use those indices to peek into the io.KeysDown[] array.
    io.KeyMap[ImGuiKey_Tab] = GLFW_KEY_TAB;
    io.KeyMap[ImGuiKey_LeftArrow] = GLFW_KEY_LEFT;
    io.KeyMap[ImGuiKey_RightArrow] = GLFW_KEY_RIGHT;
    io.KeyMap[ImGuiKey_UpArrow] = GLFW_KEY_UP;
    io.KeyMap[ImGuiKey_DownArrow] = GLFW_KEY_DOWN;
    io.KeyMap[ImGuiKey_PageUp] = GLFW_KEY_PAGE_UP;
    io.KeyMap[ImGuiKey_PageDown] = GLFW_KEY_PAGE_DOWN;
    io.KeyMap[ImGuiKey_Home] = GLFW_KEY_HOME;
    io.KeyMap[ImGuiKey_End] = GLFW_KEY_END;
    io.KeyMap[ImGuiKey_Insert] = GLFW_KEY_INSERT;
    io.KeyMap[ImGuiKey_Delete] = GLFW_KEY_DELETE;
    io.KeyMap[ImGuiKey_Backspace] = GLFW_KEY_BACKSPACE;
    io.KeyMap[ImGuiKey_Space] = GLFW_KEY_SPACE;
    io.KeyMap[ImGuiKey_Enter] = GLFW_KEY_ENTER;
    io.KeyMap[ImGuiKey_Escape] = GLFW_KEY_ESCAPE;
    io.KeyMap[ImGuiKey_KeyPadEnter] = GLFW_KEY_KP_ENTER;
    io.KeyMap[ImGuiKey_A] = GLFW_KEY_A;
    io.KeyMap[ImGuiKey_C] = GLFW_KEY_C;
    io.KeyMap[ImGuiKey_V] = GLFW_KEY_V;
    io.KeyMap[ImGuiKey_X] = GLFW_KEY_X;
    io.KeyMap[ImGuiKey_Y] = GLFW_KEY_Y;
    io.KeyMap[ImGuiKey_Z] = GLFW_KEY_Z;

    io.SetClipboardTextFn = ImGui_ImplGlfw_SetClipboardText;
    io.GetClipboardTextFn = ImGui_ImplGlfw_GetClipboardText;
    io.ClipboardUserData = window;
#if defined(_WIN32)
    io.ImeWindowHandle = (void *)glfwGetWin32Window(window);
#endif

    // Create mouse cursors
    // (By design, on X11 cursors are user configurable and some cursors may be missing. When a cursor doesn't exist,
    // GLFW will emit an error which will often be printed by the app, so we temporarily disable error reporting.
    // Missing cursors will return NULL and our _UpdateMouseCursor() function will use the Arrow cursor instead.)
    ImGuiGlfwContext ctx;
    ctx.m_Time = 0.0;
    GLFWerrorfun prev_error_callback = glfwSetErrorCallback(nullptr);
    ctx.m_MouseCursors[ImGuiMouseCursor_Arrow] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_TextInput] = glfwCreateStandardCursor(GLFW_IBEAM_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeNS] = glfwCreateStandardCursor(GLFW_VRESIZE_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeEW] = glfwCreateStandardCursor(GLFW_HRESIZE_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_Hand] = glfwCreateStandardCursor(GLFW_HAND_CURSOR);
#if GLFW_HAS_NEW_CURSORS
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeAll] = glfwCreateStandardCursor(GLFW_RESIZE_ALL_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeNESW] = glfwCreateStandardCursor(GLFW_RESIZE_NESW_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = glfwCreateStandardCursor(GLFW_RESIZE_NWSE_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_NotAllowed] = glfwCreateStandardCursor(GLFW_NOT_ALLOWED_CURSOR);
#else
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeAll] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeNESW] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_ResizeNWSE] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
    ctx.m_MouseCursors[ImGuiMouseCursor_NotAllowed] = glfwCreateStandardCursor(GLFW_ARROW_CURSOR);
#endif
    glfwSetErrorCallback(prev_error_callback);

    // Will be handled by class luisa::compute::Window
    // Chain GLFW callbacks: our callbacks will call the user's previously installed callbacks, if any.
    //    glfwSetMouseButtonCallback(window, ImGui_ImplGlfw_MouseButtonCallback);
    //    glfwSetScrollCallback(window, ImGui_ImplGlfw_ScrollCallback);
    //    glfwSetKeyCallback(window, ImGui_ImplGlfw_KeyCallback);
    //    glfwSetCharCallback(window, ImGui_ImplGlfw_CharCallback);

    get_registry().emplace(window, ctx);
    return true;
}

bool ImGui_ImplGlfw_InitForOpenGL(GLFWwindow *window) {
    return ImGui_ImplGlfw_Init(window);
}

void ImGui_ImplGlfw_Shutdown(GLFWwindow *window) {
    get_registry().erase(window);
}

static void ImGui_ImplGlfw_UpdateMousePosAndButtons(GLFWwindow *window, ImGuiGlfwContext *ctx) {
    // Update buttons
    ImGuiIO &io = ImGui::GetIO();
    for (int i = 0; i < IM_ARRAYSIZE(io.MouseDown); i++) {
        // If a mouse press event came, always pass it as "mouse held this frame", so we don't miss click-release events that are shorter than 1 frame.
        io.MouseDown[i] = ctx->m_MouseJustPressed[i] || glfwGetMouseButton(window, i) != 0;
        ctx->m_MouseJustPressed[i] = false;
    }

    // Update mouse position
    const ImVec2 mouse_pos_backup = io.MousePos;
    io.MousePos = ImVec2(-FLT_MAX, -FLT_MAX);
#ifdef __EMSCRIPTEN__
    const bool focused = true;// Emscripten
#else
    const bool focused = glfwGetWindowAttrib(window, GLFW_FOCUSED) != 0;
#endif
    if (focused) {
        if (io.WantSetMousePos) {
            glfwSetCursorPos(window, (double)mouse_pos_backup.x, (double)mouse_pos_backup.y);
        } else {
            double mouse_x, mouse_y;
            glfwGetCursorPos(window, &mouse_x, &mouse_y);
            io.MousePos = ImVec2((float)mouse_x, (float)mouse_y);
        }
    }
}

static void ImGui_ImplGlfw_UpdateMouseCursor(GLFWwindow *window, const ImGuiGlfwContext *ctx) {
    ImGuiIO &io = ImGui::GetIO();
    if ((io.ConfigFlags & ImGuiConfigFlags_NoMouseCursorChange) || glfwGetInputMode(window, GLFW_CURSOR) == GLFW_CURSOR_DISABLED)
        return;

    ImGuiMouseCursor imgui_cursor = ImGui::GetMouseCursor();
    if (imgui_cursor == ImGuiMouseCursor_None || io.MouseDrawCursor) {
        // Hide OS mouse cursor if imgui is drawing it or if it wants no cursor
        glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_HIDDEN);
    } else {
        // Show OS mouse cursor
        // FIXME-PLATFORM: Unfocused windows seems to fail changing the mouse cursor with GLFW 3.2, but 3.3 works here.
        glfwSetCursor(window, ctx->m_MouseCursors[imgui_cursor] ? ctx->m_MouseCursors[imgui_cursor] : ctx->m_MouseCursors[ImGuiMouseCursor_Arrow]);
        glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_NORMAL);
    }
}

void ImGui_ImplGlfw_NewFrame(GLFWwindow *window) {
    ImGuiIO &io = ImGui::GetIO();
    IM_ASSERT(io.Fonts->IsBuilt() && "Font atlas not built! It is generally built by the renderer backend. Missing call to renderer _NewFrame() function? e.g. ImGui_ImplOpenGL3_NewFrame().");

    // Setup display size (every frame to accommodate for window resizing)
    int w, h;
    int display_w, display_h;
    glfwGetWindowSize(window, &w, &h);
    glfwGetFramebufferSize(window, &display_w, &display_h);
    io.DisplaySize = ImVec2((float)w, (float)h);
    if (w > 0 && h > 0)
        io.DisplayFramebufferScale = ImVec2((float)display_w / w, (float)display_h / h);

    auto &&ctx = get_registry()[window];
    // Setup time step
    double current_time = glfwGetTime();
    io.DeltaTime = ctx.m_Time > 0.0 ? (float)(current_time - ctx.m_Time) : (float)(1.0f / 60.0f);
    ctx.m_Time = current_time;

    ImGui_ImplGlfw_UpdateMousePosAndButtons(window, &ctx);
    ImGui_ImplGlfw_UpdateMouseCursor(window, &ctx);
}
